WASHINGTON (Reuters/AFP) - An investigation is underway into a suspected drone strike that killed two US soldiers in Afghanistan, a US military official said on Monday. If confirmed, it would be a rare example of a friendly fire killing of US forces by the pilotless aircraft. The victims were identified as Marine Staff Sergeant Jeremy Smith, 26, and Navy Corpsman Benjamin Rast, 23. The Pentagon declined comment, saying the deaths of Smith and Rast were under investigation. But the military official, speaking to Reuters on condition of anonymity, said initial information indicated that they were killed during a Hellfire missile strike in southern Afghanistan. The official stressed that the investigation into the cause of the deaths had not been concluded. NBC News, which first reported the incident, said that the two service members were part of a unit ordered in to reinforce Marines coming under heavy fire from insurgents outside Sangin, the scene of fierce fighting for years. The Marines near Sangin, watching a video feed from the armed Predator drone overhead, saw infrared images moving towards them and may have concluded those hot spots were insurgents instead of fellow Marines, NBC reported. The investigation into last weeks incident follows a detailed account in the Los Angeles Times of a February drone strike that went terribly wrong. In the February strike, US operators of a robotic plane and special operations forces mistakenly thought a convoy of Afghan civilians in vehicles was a Taliban unit moving in. The strike near a village in Oruzgan province killed 15-16 men, one woman and three children, the US military says, while Afghans believe 23 people died, including two children. Meanwhile, the office window of the European Unions special representative to Afghanistan was hit by gunfire Tuesday, officials said. No-one was hurt in the incident at the high-security Kabul compound of envoy Vygaudas Usackas, and it is not known whether the shooting was accidental or deliberate. One high-velocity round struck the bulletproof window of head of delegation and EU special representative ambassador Vygaudas Usackas office, a statement from his office said. No-one was hurt. The incident is under investigation. It is thought that the shot was fired as Usackas was walking into his office, and that officials do not know who was responsible or where it came from. Usackas, a former foreign minister of Lithuania, was appointed to his current role last year.